You occasionally see the other side of him come out in his promos.
For awhile he was doing homophobic raps. Definitely not part of the John Cena character.
I caught part of Raw this week. During the Cena/Heyman segment, Cena's comeback to Heyman was to call him "Old and Washed Up." It's almost never cool to insult someone over something over which they have no control, in this case, age. The washed up part just isn't true. Heyman is the Manager of the current WWE champ.
When Brock finally appeared, I found myself viewing him as a Babyface coming to save Paul.
As an aside, Raw needs to cut back to two hours or less. With three hours to kill, the bits drag on endlessly. There's no way I could watch the whole show from start to finish.